Toribash
If it's 90k and the min raise is 10k you should autobuy it because you would bid 100k anyways.
Quit, probably.
If you want to just place the minimum ammount allowed you'd bet 90K.
If you want to buy it automatically and not wait until the end date you can pay 100K.
You can bet like this:

80K(Current Bid) + 10K(Minimum Raise) =
90K(Minimum Bid Allowed) < X(Your Bid) < 100K(Autobuy)

So

you can bid from 90-100K
PigeonHive Flap Buzz
No. If you bid below 100k, and no one else bids, you get the item at the end date. If you autobuy it at 100k, you get the item stariat away. How old are you, out of interest?
Quit, probably.